Devices for the cycle time-optimized molding of balloon elements from pre-extruded hose material have already been described. WO 2013/041234 describes a shaping device in which the hose blank is blown directly into a molding tool that has been flushed with a tempering medium. The hose element to be reshaped lies against the wall of the molding cavity of the primarily tempered molding tool. The molding tool comprises a hollow space that is flushed with a tempering medium and is configured with the lowest possible mass so that the particular molding temperature can be reached on the surface of the molding cavity as quickly as possible during a cyclical temperature change in the mold. In a preferred embodiment, a type of mold is described which is composed of two longitudinally divided half shells whose cavities close over the blank by being displaced from the lateral toward the blank. The tempered half shells remain closed for the duration of the blow-molding phase, i.e. during the heating and subsequent cooling of the workpiece. It is also possible for the half shell-like mold arrangement to be displaceable vertically relative to the hose blank. In the specific case described, the hose blank should be pre-tempered and/or pre-shaped before the actual blow-molding process. For this purpose, the mold moves up and down over the blank, alternatingly opening lengthwise and then closing again, over various levels of the mold. Optionally, a specific temperature corresponding to each functional level can be set in the mold. The method is suitable for the quick molding of small hose or balloon components, such as those required for common medical catheter products. However, the above method is unsuitable for large-volume components, especially long components, for components with significantly fluctuating segment diameters, for the cost-effective manufacture of long, extremely thin-walled hose components and for products manufactured in large amounts, since the mold masses required for the forming path described above tend to be relatively large and must be alternatingly tempered and/or alternatingly heated and cooled during the cycle, which is time and energy intensive.
PUR-based tire inner tubes are known commercially, and different types are available. Industrial production of the products is usually based on a continuously extruded semi-finished raw hose, which is cut to an appropriate length and the free ends of which are welded or glued directly, i.e. without a further molding step, end-to-end to create a closed ring element.
Conventional end-to-end welding of the hose ends, such as the process carried out on bicycle hoses of the type produced by Eclipse Microsystems GmbH of Ebmatingen, Switzerland, does not usually produce a visually and functionally satisfactory result. Although the joints usually exhibit sufficient mechanical reliability, the outwardly facing seam that results from the welding process is substantial in size and, apart from the appearance of the product, it could potentially affect its running properties and/or lead to a weakening of the wheel casing or the hose wall at the joint during continuous operation.
Since the raw hose material employed is normally produced by blown film extrusion, i.e. by vertical extrusion from a melt, the hose body is normally wound up as a flat band and retains this band structure throughout the rest of the processing of the product. Variations in the hose diameter and in the wall thicknesses of the hose casing usually result from the fast-running vertical extrusion. These variations can have a negative effect on the function and durability of the products.